CDE is basically like Xfce 3 or Solaris. After all, it's only a skin. Underhood, it's a modern OS (in this case Debian powered GNU/Linux). You have all the software out there plus what you can find for the CDE system (native programs seem to start with a 'dt' every one of them.
https://en.wikipedia.org/wiki/Xfce#Early_versions
